While it is safer to simply disclose when approached by a police officer anytime a person conceal carries... the "requirement" is to disclose when stopped. You can be "stopped" at any time anywhere... even while walking, shopping, farting, whatever. The key thing is to define "stop" because just talking to a cop, or him/her talking to you, about the weather, traffic, or yesterday's game, is not a "stop" but is an everyday conversation. There is no requirement to disclose during a conversation.
So how to define "stopped" when not in a vehicle? I don't know... depends on why the cop is talking to you in the first place, how things are going... cop's body language, questions asked, what is being talked about....
Of course a person could just immediately, before saying anything else, come right out and ask the officer if this is a "conversation" or is this a "stop".... and go from there.
Quite often Yooperlady and I converse with the local Chief of Police... sometimes in a restaurant, sometimes in the middle of the street in front of our house, sometimes while attending a council meeting. Now if we were required to disclose each and every time we spoke with him all of us would quickly become annoyed.
But again... it is much easier and safer to simply disclose immediately upon being approached by a LE officer regardless of the reason the officer is approaching. And I generally do disclose when meeting an officer for the first time even if we are only having a "conversation".